Sodium: the trickster ingredient making you hungry all the time

Peanuts. Popcorn. Padron peppers. One thing they all have in common is that they all taste even more delicious with lashings of salt. They may also have you glugging down more water than usual - that’s the general nutritional consensus anyway.

But actually, salty food may cause the opposite effect, according to new scientific findings studying salt intake and drinking habits. Researchers from the German Aerospace Center (DLR) and the Max Delbrück Center for Molecular Medicine (MDC) have found that salt could make you drink less… and eat more.

Does salt make you thirsty?

Nearly all of us eat too much salt. Even if you’re not reaching for the shaker every mealtime, 77% of the sodium we consume is in the food we eat before we buy it, particularly pre-packaged foods and restaurant meals.

It turns out that our bodies naturally adjust to higher salt intakes. Our kidneys generate more water, so you’re actually less thirsty after that bag of pretzels. But, all that extra sodium pulls water into your blood vessels, pumping up the volume, raising blood pressure and giving your heart extra work. The added water can lead to bloating and weight gain, but there’s also another reason it may make you pile on the pounds.

Does salt make you fat?

During 105-day and 205-day studies carried out on simulated space-flights to Mars, scientists found that subjects who ate more salt retained more water, but needed more energy. Cosmonauts on the flights had identical diets but were given three different levels of salt in their food. Every aspect of the subjects’ nutrition, water and salt intakes could be controlled and measured - experimental conditions don’t get any more pristine than this.

Scientists found that salt did indeed cause thirst in the short-term. It also led to a higher salt content in urine. But it was also triggering the kidneys to conserve water, which confused the team. Cosmonauts eating more salt during the mission complained of hunger more than those eating less salt. It was discovered that urea, a substance formed in the muscles and liver to shed nitrogen, could be involved. Synthesizing urea takes a load of energy, which explained why, in experiments on mice, those on a high-salt diet were eating more.

Urea is a crucial compound that binds to water for transportation - keeping it in our bodies and getting rid of salt. Due to the intensive energy needed to produce the substance, the mice on a salty diet didn’t need to drink more, but they did need to eat more - suggesting the need for urea-making fuel.

Once considered a waste product, it appears urea is highly useful in disposing salt and holding water. But that doesn’t mean you should use it as an excuse to load up on salt-laden French fries. Cut down your sodium levels and your body will thank you for it.